The present invention relates to an electrically operated actuator for a closure such as a slidable door of a motor vehicle.
Electrically operated actuators for sliding doors of a motor vehicle are known which include an electric motor, a clutch, and a cable drum. A cable passes around the cable drum and is connected to the slideable door. In order to control the force required to move the door, the clutch has to be capable of withstanding forces of the order of 40 Nm, and hence has to have a predetermined minimum size.
A co-pending patent application, Ser. No. 09/032, 806 filed Aug. 2, 1998 and assigned to the assignee of this invention, now U.S. Pat. No. 6,125,586 issued Oct. 3, 2000, discloses an electrically operated actuator for a slideable door of a motor vehicle that comprises a planetary gear set including a sun gear, a number of pinion gears rotatably mounted on a planet carrier and interengaging with the sun gear, and a ring gear interengaging with the pinion gears; the sun gear, planet carrier and ring gear being rotatable about an axis; an electric motor connected to the planet carrier to rotate the planet carrier about the axis; an electrically actuated brake connected to the sun gear to brake rotation of the sun gear about the axis; a cable drum rotatably driven by the ring gear; and a cable wound around the cable drum and connectable to the slideable door. The use of a planetary gear set with an electric brake controlling rotation of the sun gear means the brake need only withstand forces of the order of 10 Nm, thereby allowing the outer dimensions of the actuator to be reduced.
It is object of the present invention to provide electrically operated actuator for a closure such as a slideable door of a motor vehicle which has reduced outer dimensions comparable to the arrangement disclosed in the co-pending patent application described above.
An electrically operated actuator in accordance with the present invention comprises a planetary gear set including a sun gear, a number of pinion gears rotatably mounted on a planet carrier and interengaging with the sun gear, and a ring gear interengaging with the pinion gears, the sun gear, planet carrier and ring gear being rotatable about an axis. An electric motor is connected to the ring gear to rotate the ring gear about the axis and electrically actuated brake is connected to the sun gear to brake rotation of the sun gear about the axis. A cable drum is rotatably driven by the planetary carrier and a cable is wound around the cable drum and connected to a slideable door of a motor vehicle. The use of a planetary gear set with an electric brake controlling rotation of the sun gear means the brake need only withstand forces of the order of 10 Nm, thereby allowing the outer dimensions of the actuator to be reduced like the electrically operated actuator disclosed in the patent application described above.
The advantage of the arrangement of this invention include an increase in torque multiplication and decrease in speed. These attributes are generally desirable in electrically operated closure operators because the power source is usually a high speed, low torque electric motor.